The main characteristic of a UWB based wireless communication system is the fact that it operates as an underlay system in frequency bands already in use by other wireless communication and location (RADAR) systems. These incumbent systems will generate interference in the UWB systems (inband interference) and the UWB system will also generate interference toward these systems. Due to the very limited transmission power of the UWB systems, the range in which the generated interference will cause a degradation in the incumbent system is limited to meters or tenths of meters. An incumbent system operating in this area will also generate interference toward the UWB system in operation and thus leads to a degradation of the communication performance.
Orthogonal frequency-Division Multiplexing (OFDM) is a method of digital modulation in which a signal is split into several narrowband channels (sub-carriers) at different frequencies.
A WIMAX device operates, for example, with a bandwidth of 20 MHz at a central frequency of 3.5 GHz, whereas the frequency band of the MBOA system lies between 3.1 and 4.8 GHz.
Wireless personal area networks based on OFDM and UWB technologies like the MBOA standard may directly interfere to narrowband devices which are close to such wideband devices. At present, no specific interference mitigation techniques are implemented in the UWB standard based on OFDM (MBOA).
In order to avoid in-band spectral interference, a conventional method proposes to puncture, i.e. remove, selected sub-carriers. More precisely, this puncturing is made, taking into account channel knowledge, after the OFDM modulation in the transmitter, whereas a depuncturing is performed in the receiver before the OFDM demodulator.